Date: Wed, 04 May 2005 01:22:23 +0000 From: Chuck Robey <chuckr@chuckr.org> To: Clifton Royston <cliftonr@tikitechnologies.com> Cc: freebsd-questions@freebsd.org Subject: Re: unary operator expected Message-ID: <427823CF.6030100@chuckr.org> In-Reply-To: <20050503232643.GB13135@tikitechnologies.com> References: <AF33154333460E439B317830E50C10490D6072@tmfsrv01.muttart.org> <20050503232643.GB13135@tikitechnologies.com>
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Clifton Royston wrote:
> On Tue, May 03, 2005 at 05:13:47PM -0600, Chris Burchell wrote:
>
>>I'm working with a script written for Linux that has the following
>>lines:
>>
>># Check that networking is up.
>>[ ${NETWORKING} = "no" ] && exit 0
>
>
> I don't think it's a Linux/BSD issue. This line won't work in sh if
> NETWORKING is unset. Then you get (after parameter expansion)
>
> [ = "no" ] && exit 0
>
> which fails the syntax check.
That's a very well known mistake you ran into ... you did it wrong. You
assumed that $(NETWORKING) == NO is the same as $(NETWORKING) = ""
(empty) and they are not equal. You need to insure that $NETWORKING)
eitgher always has a value, or you have to shortcircuit the test with a
test for the variable's existence and length.
Being honest, if I were doing it, I would use NETWORKING as a macro
value, something that could immediately test the network's viability,
then operate upon that's results.
>
> I suspect "NETWORKING" always happened to be set in the Linux
> environment you were running it under, or perhaps you were using a
> different shell.
>
>
>>Can anyone help with suggestions or an alternate statement that will
>>work on FreeBSD 5.3-RELEASE?
>
>
> One time-honored idiom is:
>
> [ "X${NETWORKING}" = "Xno" ] && exit 0
>
> or you can just make sure that NETWORKING always gets set to some
> value.
>
> -- Clifton
>
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